Research highlights: Dr. Róisín Commane likely has more frequent flyer miles than you. As part of the joint NASA/Harvard University Atmospheric Tomography Mission (ATom), Dr. Commane just completed her fourth series of global flights aboard NASA’s four-engine DC-8 research aircraft. Flying as high as 40,000 feet to skimming the surface at 500 feet (check out the amazing videos of low-level flights over Arctic sea ice and the open ocean on the ATom Twitter feed), ATom instruments collected data about chemical components of the atmosphere between 85° north and south latitude.

Dr. Commane aboard NASA’s DC-8 research aircraft during
ATom. Each ATom deployment followed similar flight tracks in a
counter-clockwise direction: from Alaska south over the Pacific Ocean to New Zealand, east
across the southern tip of South America, north over the Atlantic Ocean to
Greenland, then west over the Arctic Ocean back to Alaska. Dr. Commane notes
that the counter-clockwise direction of travel makes use of tailwinds on the
long flight from New Zealand to Chile. Photo by Dr. Bernadett Weinzierl, Univ.
of Vienna, and courtesy of Dr. Commane.

To say these flights were frill-free might be an understatement. Flights often lasted 10 hours or longer and the aircraft, which was built in 1969 and acquired by NASA in 1985, is a flying laboratory with instruments receiving priority over people (or soundproofing—headsets are recommended to “save your ears,” according to the ATom daily schedule mission planning page). A typical “day” for Dr. Commane during the recently-completed fourth and final ATom deployment might begin well before local sunrise for flight preparations and end after sunset several time zones later, a schedule that was repeated throughout the almost one-month series of flights conducted between April 24 and May 21, 2018.

The “T” in “ATom” stands for tomography. Tomography is a technique for imaging by sections or sectioning using any kind of penetrating wave (magnetic resonance imaging, or MRI, is a type of tomography that uses strong magnetic fields and radio waves to create high resolution images of soft tissue in the human body that can be looked at slice by slice). ATom uses 24 aircraft-mounted instruments to sample slices of the atmosphere and analyze the chemical composition of these slices. These data are used to study the impact of human-produced air pollution on greenhouse gasses and on chemically reactive gasses in the atmosphere, especially over remote ocean areas. Data from ATom are helping to validate and improve satellite and model atmospheric data as well as the algorithms used to produce these data. Between the summer of 2016 and this past spring, Dr. Commane participated in ATom flights that sampled the atmosphere in all seasons.

Dr. Commane is a co-investigator for the Harvard University-develped Quantum Cascade Laser System (QCLS) instrument. The QCLS measures atmospheric concentrations of carbon monoxide (CO), methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2). She uses a range of tools, including airborne gas concentration data, atmospheric transport models, and ecosystem models, to develop a better understanding of processes occurring on Earth’s surface that affect atmospheric chemistry. She is particularly interested in the different chemical signatures created by fires occurring in Africa and how these fires affect the chemical composition of the atmosphere over the Atlantic Ocean. She also is examining how clouds in the Arctic can hide the chemical signature of fires and make them more difficult to detect.

ATom researchers, in turn, use satellite data to extend the data collected from their airborne observations to a global scale and deliver a single, large-scale, contiguous in situ dataset that can be used for evaluating and improving computer models designed to forecast atmospheric conditions. One such model is the Goddard Earth Observing System Model, Version 5 (GEOS-5), which is located at NASA’s Goddard Space Flight Center in Greenbelt, MD.

Much of the ATom data collected by Dr. Commane and her colleagues are being archived at the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC). ORNL DAAC is the Earth Observing System Data and Information System (EOSDIS) DAAC responsible for archiving and distributing NASA Earth observing data related to biogeochemical dynamics, ecology, and environmental processes.

While Dr. Commane and her ATom research colleagues are still finalizing mission data and digging into science questions, she notes that they have been really impressed at how well the GEOS-5 atmospheric forecast has predicted pollution. In looking specifically at comparisons between GEOS-5 model predictions and observed concentrations of atmospheric CO, for example, she points out that some events, like Siberian forest fires, were completely missed by the model due to Arctic clouds masking the fires. Overall, though, she and her colleagues found that the model accurately predicted both the location and magnitude of atmospheric pollution plumes.

The real strength of ATom, observes Dr. Commane, will be when all the mission data are final and complete, giving the research community data representing all four seasons that can be used to evaluate and improve atmospheric chemistry models on a global scale. For a frequent flyer like Dr. Commane, these data are a price worth paying for her long days in the air.